Corrosion is often a serious issue in oil- and gas field processes, e.g. in transportation of crude oil, and in oil or gas wells. This could be due to dissolved gases such as carbon dioxide or hydrogen sulfide causing so-called sweet and sour corrosion, respectively, on ferrous metal surfaces. Another serious source of corrosion is the often high electrolyte concentrations in the water which is co-produced with the oil and gas. Further, severe risks of corrosion are obvious when inorganic or organic acids are used in so-called acid stimulation or fracturing operations encountered in order to increase the productivity of oil and gas wells. Also in drilling operations there often is a need to use corrosion inhibitors, e.g. in drilling fluids. Corrosion problems are also often an issue in downstream processes, such as refineries, when e.g. salts or acid components from crude oils being processed are causing corrosion of ferrous metal.
Different types of nitrogen-containing compounds, such as e.g. fatty amines, alkoxylated fatty amines, amidoamines, and quarternary ammonium compounds, are well-known bases for corrosion inhibitor formulations used in various kinds of systems.
U.S. Pat. Nos. 5,352,377 and 5,456,731, for example, disclose reaction products of hydrocarbyl-substituted carboxylic anhydrides, more specifically hydrocarbyl-substituted succinic anhydrides, and aminoalkanols, e.g. ethoxylated fatty alkyl monoamines or ethoxylated fatty alkyl propylenediamines, that can provide effective antiwear, antirust, and corrosion-inhibiting properties in lubricant and fuel applications.
U.S. Pat. No. 5,178,786 relates to corrosion-inhibiting compositions and their use in functional fluids, especially aqueous hydraulic fluids. These compositions comprise at least four components A, B, C, and D, where component D is an ester-salt formed by the reaction of an alkyl or alkenyl succinic anhydride with an alkanolamine. The preferred alkanolamines are, e.g., dimethylethanolamine, diethylethanolamine, and methylethylethanolamine, and thus the preferred products D are not polymers.
There are also a number of patent publications where oligomeric/polymeric nitrogen-containing ester-linked compounds based on dicarboxylic acids/anhydrides and ethoxylated (fatty alkyl)amines are used in other applications/systems. For example, in EP 0 572 881 a product obtained from an oxyalkylated primary fatty amine and a dicarboxylic acid is disclosed for use in a process for separation of a petroleum emulsion of the water-in-oil type. U.S. Pat. No. 4,781,730 discloses reaction products of a polybasic acid and a polyhydroxyalkanolamine that are components in a fuel additive composition for reduction of valve seat recession in a vehicle. U.S. Pat. No. 5,034,444 discloses a rheological additive for non-aqueous coating compositions that may be the reaction product of an alkoxylated aliphatic nitrogen-containing compound and an organic polycarboxylic anhydride or acid. EP 0 035 263 A2 discloses polyester compounds produced by reaction between a dicarboxylic acid and an alkoxylated tertiary amine and their use as textile softeners. U.S. Pat. No. 5,284,495 discloses oligomers/polymers, which can be prepared by polymerising an anhydride, e.g. phthalic anhydride, and long-chain amine containing diols, e.g. ethoxylated octadecylamine. These products are used as additives that improve the low-temperature properties of distillate fuels. U.S. Pat. No. 5,710,110 discloses a drilling fluid composition containing an oil well fluid anti-settling additive, which is a reaction product wherein the reactants are one or more alkoxylated aliphatic amino compounds and an organic polycarboxylic anhydride or acid.
In the non-prepublished patent application PCT/EP2010/059325 polymeric products obtainable by the reaction of an alkoxylated fatty amine with a dicarboxylic acid derivative, optionally quaternised, are described. The said products are used for corrosion inhibition, but have a different structure and performance than the products of the present invention.
Although a variety of corrosion inhibitors to be used in the presence of freshwater, seawater, or brine have been developed, there is still a need for more effective corrosion inhibitors, especially if these also can be shown to fulfill stringent regulatory requirements for environmental adaptation. Thus, there is a great need for new corrosion inhibitors with an acceptable biodegradation profile combined with a low disposition to bioaccumulation and an excellent technical performance.